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/*
 * Copyright 2013-2021 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.cloudfoundry.reactor.doppler;

import io.netty.buffer.Unpooled;
import io.netty.handler.codec.DelimiterBasedFrameDecoder;
import io.netty.handler.codec.http.HttpHeaderNames;
import java.io.IOException;
import java.io.InputStream;
import java.nio.charset.Charset;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import reactor.core.publisher.Flux;
import reactor.netty.ByteBufFlux;
import reactor.netty.http.client.HttpClientResponse;

final class MultipartCodec {

    private static final Logger LOGGER = LoggerFactory.getLogger(MultipartCodec.class);

    private static final Pattern BOUNDARY_PATTERN = Pattern.compile("multipart/.+; boundary=(.*)");

    private static final int MAX_PAYLOAD_SIZE = 1024 * 1024;

    private MultipartCodec() {}

    static DelimiterBasedFrameDecoder createDecoder(HttpClientResponse response) {
        String boundary = extractMultipartBoundary(response);

        return new DelimiterBasedFrameDecoder(
                MAX_PAYLOAD_SIZE,
                Unpooled.copiedBuffer(
                        String.format("--%s\r\n\r\n", boundary), Charset.defaultCharset()),
                Unpooled.copiedBuffer(
                        String.format("\r\n--%s\r\n\r\n", boundary), Charset.defaultCharset()),
                Unpooled.copiedBuffer(
                        String.format("\r\n--%s--", boundary), Charset.defaultCharset()),
                Unpooled.copiedBuffer(
                        String.format("\r\n--%s--\r\n", boundary), Charset.defaultCharset()));
    }

    static Flux decode(ByteBufFlux body) {
        return body.asInputStream().skip(1).doOnDiscard(InputStream.class, MultipartCodec::close);
    }

    private static void close(InputStream in) {
        try {
            in.close();
        } catch (IOException e) {
            LOGGER.warn("Could not close input stream. This will cause a direct memory leak.", e);
        }
    }

    private static String extractMultipartBoundary(HttpClientResponse response) {
        String contentType = response.responseHeaders().get(HttpHeaderNames.CONTENT_TYPE);
        Matcher matcher = BOUNDARY_PATTERN.matcher(contentType);

        if (matcher.matches()) {
            return matcher.group(1);
        } else {
            throw new IllegalStateException(
                    String.format(
                            "Content-Type %s does not contain a valid multipart boundary",
                            contentType));
        }
    }
}